Synthetic parathyroid hormone, manufactured by Eli Lilly and sold in the United States under the brand name Forteo, is the only FDA approved osteoporosis drug shown to directly stimulate bone formation. (Other treatments work by interfering with the process of bone loss.) However, this medication requires administering a daily injection - something many osteoporosis patients are unwilling or even unable to do. And others who might benefit begin taking the medicine, but fail to complete the course of treatment because of the onerous process or discomfort at the injection site.

As a result, a number of different laboratories are investigating other ways for patients to take in this potent medication. On April 16, Zelos Therapeutics, a pharmaceutical company specializing in bone disorders, announced a partnership with Aegis Therapeutics to develop a nasal spray to deliver parathyroid hormone.

Nasal Spray for Parathyroid Hormone

"We think it will be an improvement over Forteo," says Jay Mohr, chief business officer for Zelos, noting that the new synthetic parathyroid hormone will have a different chemical structure from the one currently on the market. "The technology will produce greater bone formation effects, especially for patients with more severe osteoporosis."

Aegis, a drug delivery company, has developed a device designed to ensure that the liquid nasal spray is not inhaled, and the drug would not reach the lungs, according to Ralph Baer of Aegis. Instead, the spray would be absorbed by the mucus membranes inside the nose, allowing the medication to pass directly into the bloodstream. The goal of the device, Baer says, would be to "administer it non-invasively so you don't have to use a needle to take the drug."

Mohr says that Zelos expects to submit its new drug to the FDA by the end of 2011, with the goal of reaching
the market in
in 2012.

PTH as a Pill

Separately, Bone Medical Limited, an Australian pharmaceutical company, is now working on an oral version of synthetic parathyroid hormone. The medication, in the form of a capsule that would be taken daily, is being developed for marketing worldwide, including eventual submission to the FDA for approval.

The oral delivery technology Bone Medical is using differs from other approaches because it only uses known chemical entities to achieve its effects. Efforts by other groups to create an oral formulation
are attempting to combine parathyroid hormone with
new, untested compounds
in order to increase its bioavailability, meaning the body's capacity for using it. According to Dr. New, using such chemicals
may create toxicological issues. This means that the Bone Medical medicine, known as CaPTHymone, should
pass through the regulatory process much more rapidly.

In a trial with volunteers, eight postmenopausal women took a single dose of the medicine and experienced increases in calcium blood level comparable to those seen for patients taking Forteo. "If everything goes smoothly, three years would be a reasonable time horizon," says Dr. Roger New, the chief scientific officer working on the drug in London.

The new medicine is also expected to be stable at room temperature, thus avoiding the refrigeration requirement of Forteo. Dr. New points out that taking parathyroid hormone by mouth could help increase compliance for osteoporosis patients who are considered candidates for the drug.
"Some people when they hear they have to take injections refuse to take them at all," he says.

Before long, patients who are candidates for parathyroid hormone -- but don't want the needles -- may be able to choose from among other options for their treatment.